The adage "photos don't lie" is no longer reliable. The advent of digital editing tools makes it relatively easy to move, add, or delete features from photographs. Other digital content is similarly susceptible to alteration.
In accordance with a preferred embodiment of the present invention, this problem is at least partially overcome by providing a photograph with supplemental data. This supplemental data is below a threshold of human perception (e.g., is essentially invisible) yet can extend throughout the image. (In some embodiments the supplemental data is adaptively scaled to correspond to characteristics of the associated image.) If a version of the image is thereafter encountered with the supplemental data missing or attenuated, the image is known to have been altered. By reference to such supplemental data, it is often possible to identify particular regions within the image that have been altered.
The foregoing and additional features of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.